The present invention relates to an electronic apparatus powered by a replaceable battery or a rechargeable battery and, more particularly, to an electronic apparatus capable of alerting the user to the residual amount of a battery capacity.
The prerequisite with an electronic apparatus powered by a battery is that it be protected from errors in the event of the voltage drop of the battery. For this purpose, such an apparatus is provided with a detecting circuit responsive to the drop of the battery voltage to below a predetermined value, and an alerting device for urging, in response to the output of the detecting circuit, the user to replace the battery by a visible or audible indication.
Electronic apparatuses having the alerting device mentioned above are disclosed in the various documents, as follows. Japanese Patent Laid-Open Publication No. 4-191914 teaches a battery-powered computer having a detecting circuit responsive to the run-down of a battery. When the battery runs down as detected by the detecting circuit, a cursor appearing on a display has an attribute thereof changed to inform the user of the run-down. Japanese Patent Laid-Open Publication No. 4-36818 proposes an electronic apparatus having a display implemented as two light emitting diodes of different colors. The light emitting diodes are selectively turned on display the voltage drop of a battery to below a predetermined value in three consecutive steps. Japanese Patent Laid-Open Publication No. 4-236379 discloses an electronic apparatus capable of computing the residual amount of the capacity of a secondary battery and displaying it. Further, Japanese Patent Laid-Open Publication No. 2-295385 allows a television receiver or similar electronic apparatus having an audio function to alert the user to the run-down of a battery with an audible message.
As stated above, it has been customary with an electronic apparatus to use a display thereof in alerting the user to the remaining life of a battery. A television receiver or similar electronic apparatus having an audio function is exceptional in that it produces an audible alert message. This cannot be done with, for example, portable computers and electronic pocketbooks which lack an audio function. However, the problem with the alert relying on a display is that the user is apt to manipulate the apparatus without noticing the alert and becomes unable to operate it halfway. This problem occurs, for example, when the user is away from the apparatus when the alert appears on the display or when the user operates the apparatus, e.g., a computer for musical applications without watching the display.
Usually, alerting means of the kind described generates an alert just before the apparatus is fully disabled. Therefore, when the alert occurs in the midst of an operation needing a long period of time and inhibiting an interruption, the user is often prevented from taking an adequate measure immediately despite that the user is aware of the alert. While the alert representing the residual amount of the battery may be displayed either constantly or periodically, such an alert is wasteful in most cases and, moreover, gives the user an unfavorable impression as to the reliability of the apparatus. Although the alert using voice is free from this problem, it also prevents the user from taking an adequate measure when produced just before the stoppage of the apparatus.